The electrical industry uses an antioxidant to help keep electrical connections from getting oxidation in-between the conductive surfaces of the connections. An antioxidant may be particularly important when the connection is made through an aluminum to aluminum or an aluminum to copper connection.
In particular, most metals (with a few exceptions, such as gold) oxidize freely when exposed to air. In the specific case of aluminum, aluminum oxide is not an electrical conductor, but rather an electrical insulator. Consequently, the flow of electrons through the oxide layer can be greatly impeded. However, because the oxide layer is only a few nanometers thick, the added resistance is not noticeable under most conditions. When an aluminum wire is terminated properly, the mechanical connection breaks the thin, brittle layer of oxide to form an excellent electrical connection. Unless this connection is loosened, there is no way for oxygen to penetrate the connection point to form further oxide, and thus the connector operates with little change.
However, as is typically the case, this connection does loosen over time, and once oxygen penetrates the connection point to form an oxide, the electrical connection may be compromised. For instance, aluminum, steel, copper, each expand and contract at different rates under thermal load, so connections utilizing multiple metals can become progressively looser over time. In one instance, the expansion/contraction cycle results in the connection loosening slightly, overheating, and allowing intermetallic steel/aluminum oxidization to occur between the conductor and the screw terminal. This may result in a high-resistance junction, leading to overheating.
Another issue is the joining of aluminum wire to copper wire. As aluminum and copper are dissimilar metals, galvanic corrosion can occur in the presence of an electrolyte and these connections can become unstable over time.
To prevent oxidation, many types of antioxidants have been developed in the industry. These antioxidants, however, are typically either a grease or gel-like material. For example, in one instance, a twist-on connector, such as a Twister® Al/Cu Wire Connector, available from Ideal Industries, Inc., Sycamore, Ill., has been designed for the purpose of joining aluminum to copper wire. This twist-on wire connectors use a special polypropylene, zinc plated steel, antioxidant grease to prevent corrosion of the connection. In another example similarly available from Ideal Industries, a grease-like antioxidant includes a polybutene (<80% wt), zinc dust (20% wt), and silicon dioxide (<5% wt).
While the prior antioxidants are oftentimes suitable for their intended purposes, there remains a need for a malleable antioxidant for use with some electrical connections.